My Nauticam housing came with a standard friction-fit port cover. A plastic affair that kinds pops into the port opening.
Nauticam has recently released an upgrade to this cover! They took the bayonet fitting that comes on all of their standard ports (dome ports, flat ports, etc.) and molded it to the plastic pop-in cover.
The result is simply a cover that won't pop out!!
This also likely offers a bit of protection to the port locking mechanism, and assures I store and travel with the red port release lever in the stowed position.
There is no O-ring on this - it is not a water-tight seal. It should probably say that on the cover (like the Ikelite's did / do) - but this is a big upgrade. I pack my housing in with a bunch of other stuff, and the peace of mind of knowing this cover is locked in place makes it well worth the upgrade.
Thanks to Ryan at Reef Photo, and the good folks at Nauticam.
Here are some shots.
-Ken
The two covers side by side. New on the left, original on the right

Details of the New cover

Original cover

They both fit the housing the same - except one won't pop off!
New Cover

Original cover.

Instructions on the new cover.
